Among Ultra Wide Band (UWB) wireless communication technologies which have made a remarkable advancement for the last few years, a chaotic UWB wireless communication technology performs a communication by using UWB signals based on a Chaos Theory, which will be referred to as chaotic signals, hereinafter. Conventional narrow-band wireless communication technology requires an intermediate frequency (IF) up-converter and an IF down-converter to convert the frequency of baseband signals and transmit/receive digital data over an ultra high frequency of several GHz. However, with the chaotic UWB wireless communication technology, it is possible to form a UWB signal spectrum without the IF up-converter and IF down-converter to thereby realize a communication system having a simple functional structure.
A chaotic signal generator generating the UWB signal spectrum can be realized in the form of a chaotic oscillator. Researchers have been studying chaotic oscillators theoretically since 1980s. In 1993, the chaotic oscillators have become widely known as a Chua's circuit is introduced. However, the transformation possibility of a circuit or a device has been obscure in the Chua's circuit.
A first related art disclosed in an article by A. S. Dmitrev et al., entitled “Ring oscillating systems and their application to the synthesis of chaos generators,” International Journal of bifurcation and chaos in applied science and engineering, vol. 6, pp. 851-865, May 1996, analytically provides an UWB signal generation process complementing shortcomings of the Chua's circuit. According to the first related art, signals generated in a non-linear device pass through primary and secondary low pass filters (LPFs) and then fed back into the non-linear device. The feedback signals oscillate in a wide frequency band. According to the first related art basically, wideband signals are generated based on a filter coefficient in an oscillation frequency of each filter. The wideband signals are UWB signals having a center frequency of several GHz and a bandwidth of over hundreds of MHz.
A second related art by A. S. Dmitrev et al., entitled “Ultra wideband direct chaotic communication for low bit rate information transmission,” Technical Physics Letters, Vol. 29, pp. 22-74, January 2003, realizes a chaotic UWB wireless communication system based on the first related art. The chaotic UWB wireless communication system of the second related art includes a chaotic oscillator, a detector, an analog-to-digital converter, and a baseband processor, and it operates in a bandwidth from 2 GHz to 4 GHz.
However, the chaotic UWB wireless communication system can hardly control the frequency band of the chaotic signals, and it shows a low detection performance because it adopts a conventional on/off keying method.
A conventional communication protocol for measuring a range between devices is already defined. FIG. 1 describes the conventional communication protocol for measuring a range between devices. According to the conventional communication protocol, a range is measured by transmitting a packet from a node 1 to a node 2 and calculating a round trip time of the packet returning from the node 2 back to the node 1. In short, a round trip time T of a packet is calculated by measuring a time T_prop1 which is taken for the packet to be transmitted from the node 1 to the node 2, a time T_process which is taken for the packet to be processed in the node 2, and a time T_prop2 which is taken for the packet to be transmitted from the node 2 to the node 1. Herein, T=T_prop1+T_process+T_prop2. The moment when the packet arrives at the node 2, the moment when the packet process is completed at the node 2, and the time when the packet arrives at the node 1 are based on a leading edge, which is a moment when the first data of a packet payload arrive following a packet header. A range R is measured based on the following Equation 1 and the acquired total round trip time T of the packet.R=C*(T−T_process)/2  Eq. 1
where C denotes a propagation speed.
An exact leading edge should be acquired to measure the range precisely based on the Equation 1.
However, no communication system having a range measurement function has been suggested in connection with the conventional chaotic UWB wireless communication technology.